275/55R21 in inches

A 275/55R21 tire is 32.9″ tall and 10.8″ wide, and fits a 21″ wheel. In inches it is written 32.9×10.8R21.

Diameter32.91″

Width10.83″

Sidewall5.95″

Drawn to scale. Nominal dimensions calculated from the size code.

Manufacturer data

How tall 275/55R21 tires really are

Heights published by Michelin for the one tire in this size. Their published revolutions per mile work out to 31.9″ under load (below).

The one tire listed, the Michelin Defender LTX M/S 2, measures 32.90″: 0.01″ shorter than the size code's 32.91″.

Height under load31.9″

Published revs per mile (633) mean the tire rolls like a 31.9″ tire on the vehicle. Use this for speedometer calibration.

1 tire in 275/55R21

Sort by the spec you care about.

	Load					Revs/mi	Source
Michelin Defender LTX M/S 2All-season	XL · 116H	32.90	39.2	11.0	2,756	633	Spec page

Is 275/55R21 a 33-inch tire?

≈33″

Yes. The size code works out to 32.91″, and the 1 tire here publishes 32.90″, so people call it a 33.

All 33-inch tire sizes, on every wheel size.

Compare with nearby sizes

Differences in overall diameter, calculated from each size code.

Size	Diameter ″	vs 275/55R21	Difference
295/55R20	32.78	-0.13″	-0.4%
305/45R22	32.81	-0.10″	-0.3%
275/50R22	32.83	-0.08″	-0.3%
275/60R20	32.99	+0.08″	+0.3%
33×11.50R20	33.00	+0.09″	+0.3%
33×12.50R20	33.00	+0.09″	+0.3%
33×13.50R20	33.00	+0.09″	+0.3%
33×12.50R22	33.00	+0.09″	+0.3%
355/40R22	33.18	+0.27″	+0.8%
305/55R20	33.21	+0.30″	+0.9%

How to read 275/55R21

How to read any tire size

How 275/55R21 116H is printed on the sidewall. It's the most common code among the 1 tire here; tires in this size come in other load and speed ratings too.

1275Section width

275 mm across the widest point, or 10.83 inches. Every 275 size

255Aspect ratio

A percentage, not a measurement: the sidewall is 55% as tall as the tire is wide, which is 151.3 mm or 5.95 inches.

3RConstruction

Radial construction.

421Wheel diameter

Mounts on a 21-inch wheel. Approved wheel widths run 7.5″ to 9.5″.

5116Load index

Each tire carries up to 2,756 lb (1,250 kg) at its maximum pressure.

6HSpeed rating

Rated for up to 130 mph sustained.

XLExtra load

Printed after the size.

Specification	Inches	Metric
Overall diameter	32.91	836 mm
Section width	10.83	275 mm
Sidewall height	5.95	151.3 mm
Circumference	103.4	2,626 mm
Revolutions per mile (calculated, unloaded)	612.8	381 per km
Revolutions per mile (published by manufacturers)	633	393 per km
Approved wheel width	7.5–9.5	191–241 mm

Questions about 275/55R21

What is 275/55R21 in inches?

32.91 inches tall, 10.83 inches wide, on a 21-inch wheel. Written in inches, that is roughly 32.9×10.8R21.

What wheel width do I need for 275/55R21?

Manufacturers approve 7.5–9.5″ wide wheels for this size.

How many revolutions per mile does a 275/55R21 make?

Published figures run 633 revolutions per mile. The calculated figure is 612.8, but manufacturers measure the tire under load, where it rolls on a smaller radius.